Re: SPICE files

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Dave Lewis <hvdave-at-earthlink-dot-net> 

Yes linear as far at the capacitors go.  The non-lineararity I speak of
is due to the miller effect and the drain voltage wave shape.  These can
result in lots of non-linear kinds of things to show up on the
waveforms, like for example, the step commonly seen on the gate turn on
voltage at threshold.   To me thats a non-linear effect but possibly
others might see it differently.

The modeling of high frequency power converters I've done rarely calls
for any kind of accurate Mosfet model.  Normally I just slap in a bunch
of IRF250s and go.   My main goal is just trying to work out the
transfer functions, waveforms, and component stresses before
breadboarding.   Other applications may call for much more precision,
like an RF power amplifier.

Dave Lewis



Tesla list wrote:
 >
 > Original poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br>
 >
 > Tesla list wrote:
 >  >
 >  > Original poster: Dave Lewis <hvdave-at-earthlink-dot-net>
 >  >
 >  > You can just add a cap between gate and drain of the appropriate value
 >  > to the model.  That will simulate the miller capcitance pretty well.
 >  > Check the data sheet to see what value makes sense.  Miller capcitance
 >  > is really the one that matters as far as non-linearity goes.
 >
 > This would result in a completely linear model for the capacitances.
 > Ok if you want qualitative results.
 > Take a look at the SwitcherCAD simulator, available at www.linear-dot-com
 > The documentation says that the models for power mosfets are very
 > accurate, with all the nonlinear capacitances.
 >
 > Antonio Carlos M. de Queiroz